Field of the Invention
The invention relates to an electromagnetic valve for controlling the flow of a pressure medium.
Background of the Invention
Such Actively adjustable damping systems that are designed for vehicles and that usually operate on the principle of a variable opening cross section are well-known. Such dampers (shock absorbers) adjust the corresponding shock damping characteristics by means of hydraulic proportional valves and can be adapted to a wide range of driving situations, for example, with respect to the surface of the road lane or to various customer specifications. The proportional valves continuously control the fluid flow in the damper by means of a movable slide, which is moved by a solenoid coil. The proportional valve's cross section, through which the oil flows, changes as a function of the energization of the electromagnetic proportional valve.
EP 1 657 431 A1 discloses a generic electromagnetic valve as a slide valve, in which the valve slide, which is disposed in a slide channel of a valve body in such a way that said valve slide can be displaced, consists of a hollow cylindrical slide portion, which takes over the slide function, and an adjoining armature portion, which is in magnetic operative connection with a pole core.
According to this EP 1 657 431 A1, the region of the hollow cylindrical slide portion has radial apertures, which release or close the radial passage openings of the valve body as a function of the position of the valve slide in the slide channel, so that the fluid is allowed to flow through the valve by way of a fluid inlet port on the slide channel into the cavity of the hollow cylindrical slide portion and by way of its apertures in the passage openings, which are designed as the fluid outlet port; or said fluid flow through the valve is blocked. In the de-energized state of the solenoid coil, a compression spring exhibiting a linear characteristic between the pole core and the valve slide pre-stresses the said valve slide into a basic position that closes the passage opening.
In addition to continuously adjustable damping systems, damping systems having a damping characteristics that can be adjusted in discrete stages are also well-known. However, damping systems of this type that comprise the electromagnetic slide valves known from the prior art can only be implemented with inadequate properties. It has been demonstrated that if a helical spring with a linear characteristic is used, then it will not be possible to steer the valve slide into a central position between the basic settings, which release or close the passage openings, and to maintain this central position by energizing the solenoid coil with an average current intensity.
Therefore, the object of the present invention is to provide an electromagnetic valve that is designed to control the flow of a pressure medium and that is suitable for adjusting in discrete stages the damping characteristic of a damping system, especially a shock absorber (damper) of a vehicle.
This engineering object is achieved by means of an electromagnetic valve exhibiting the features disclosed herein.